IMPACT OF AGRICULTURAL WATER ALLOCATION ON THE ECOSYSTEMS IN THE INNER NIGER RIVER DELTA

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1 International Journal International of GEOMATE, Journal Feb., 218 of Vol.14, GEOMATE, Issue 42, Feb., pp Vol.14, Issue 42, pp Geotec., Const. Mat. & Env., DOI: ISSN: (Print), (Online), Japan IMPACT OF AGRICULTURAL WATER ALLOCATION ON THE ECOSYSTEMS IN THE INNER NIGER RIVER DELTA *Barry Kassambara, Homayoon Ganji and Takamitsu Kajisa Graduate School of Bioresources, Mie University, Japan Corresponding Author, Received: 9 June. 217, Revised: 22 Aug. 217, Accepted: 16 Jan. 218 ABSTRACT: The Niger River is a lifeline for humans and biodiversity in Africa s Sahelian region. Owing to climate change and population increase over the past three decades, the inhabitants of the Sahel have witnessed that their ecosystem is under threat, and a significant reduction of its resources has occurred, particularly in the Inner Niger Delta. In the recent years, because of the Malian government s policy of developing large-scale irrigation, a sustained rate of expansion of around 5, ha of new reclamation area has been seen each year in Office du Niger located upstream of the Inner Delta. The expansion of annual rice double cropping and sugarcane cultivation constitute the main factors for the reduction of the water resources downstream in this Delta. This paper analyzes the hydrological impacts of this large-scale irrigation and crop pattern on the floodplain of the Inner Delta during high-flow and low-flow periods. The study results indicated that despite the rainfall and recent increases in upstream flows of the Niger River, the flooded area size has reduced. We could confirm that the annual average water-withdrawal proportion barely changed during the high-flow period but changed significantly during the low-flow period when the size of the paddy rice and sugarcane area increased. Therefore, changing the crop pattern toward vegetables instead of paddy rice and sugarcane during the low-flow period might be a solution. Keywords: Office du Niger, Inner Delta, Irrigation, Ecosystems 1. INTRODUCTION The Republic of Mali is a landlocked country in West Africa; it is the eighth-largest country in Africa, with an area of 1,241,19 km² and a population of approximately 16.8 million (213). According to the UNDP report (215), 5.6% of the population lives below the income poverty line ($1.25/day), and 1.8% lives in nearmultidimensional poverty [1]. With 8% of its population engaged in agricultural activities, this sector is the cornerstone of Mali s economy and shows great potential to drive economic growth. Over 31% of the population is exposed to food insecurity [2]; however, only 7% of 43.7 million hectares of arable land is currently cultivated. Potential irrigable lands that are currently developed correspond to 2.2 million hectares or 14% of the total [3]. Approximately half of Africa s total wetland area comprises floodplains. These include famous large-scale examples, such as the Inner Niger Delta in Mali, the Okavango Delta in Botswana, the Sudd of the Upper Nile in Sudan and the Kafue Flats in Zambia, that cover several thousand square kilometers [4]. Beyond the town of Ségou, the Niger River forms a vast inland delta (41,8 km²); it joins with its main tributary, the Bani, at Mopti and then forms several lakes. The watershed area of this 164 Inner Delta covers 13, km². The rapid expansion of irrigation upstream in Office du Niger, irrigated only by the diversion dam of Markala, has had a significant impact on the availability of water resources in the Niger River and its associated delta downstream. To address this problem, this investigation analyzes the historical variation of the Niger River hydrology and the evolution of irrigated areas and seasonal crop patterns in Office du Niger, which is by far the largest water user. The objectives of this study are twofold: 1) to analyze the Niger River discharge and rainfall, and 2) to evaluate the irrigated land and seasonal crop pattern water use of Office du Niger and its impact on the flooded area of the Inner Delta. 2. FIELDS AND METHODS 2.1 Study Area The Niger River Basin in Mali The Niger is the main river in Western Africa; it extends approximately 4,185 km (2,6 mi), of which 1,7 km (1,6 mi) flows through Mali (Fig. 1). Its source is in the southeastern part of the Guinea Republic, and the total catchment area of the Niger River is 2,117,7 km² (817,6 mi²). In the 196s, the independent countries (Benin,

2 International Journal of GEOMATE, Feb., 218 Vol.14, Issue 42, pp Burkina Faso, Cameroon, Côte d Ivoire, Republic of Guinea, Mali, Niger, Nigeria, and Chad) of the Niger River Basin decided to coordinate their efforts to use natural resources with a priority on water resources. The Commission of the Niger River was renamed the Niger Basin Authority (NBA) on November 21, , is a diversion dam used to irrigate the surrounding area of Office du Niger. In the past, no scientific research was conducted specifically on the influence of agricultural land expansion and seasonal crop pattern in Office du Niger on the river flow in the Inner Delta. The former studies mainly focused on the hydrological regime and the influence of climate change [6-8] Office du Niger Agricultural Area The irrigation area of Office du Niger is located at the death Delta delta mort, an ancient branch of the Niger River in the westerly region of the Inner Niger Delta delta vif. This irrigation zone covers a gross area of 2,458,56 ha with an irrigable area of 1,947,46 ha. 1,445, ha are fed by gravity-assisted water from the Markala dam, and by 215, only 138, ha were developed. 2.2 Data Collection Fig.1 Niger River and Inner Delta in Mali. In Mali, the Sélingué dam located upstream on the Niger River has been used for hydropower since The Markala dam, which opened in The data for water flow, rainfall, irrigated land water use, seasonal crop pattern, and aerial photographs were obtained from different sources. The data sources are listed in Table 1. Table 1 Data type and data sources No. Stations Source Date Data type Reference 1 2 Mopti meteorological Koulikoro, Ke- Macina, Mopti, Akka, and Dire Malian Meteorological Service Malian Government Hydraulic Service Office du Niger Malian Government Hydraulic Service Annual rainfall Water flow Irrigated land, seasonal crop pattern and water use Remote sensing data (Landsat images, 214) and aerial photographs Fig. 2, Fig. 3, Fig. 6 Fig. 4, Fig. 5, Fig. 6 Fig. 8, Fig. 9 Fig Calculation Procedures Hydrologic data analysis The correlation coefficient between rainfall and river flow reflects the degree of linear association between rainfall and river discharge [5]: rr XX,YY = ss XX,YY = 1 ss XX ss YY NN 1 NN ii=1 (xx ii xx )(yy ii yy ) (1) ss XX ss YY Where the standard deviation is ss 2 = 1 NN 1 (xx ii xx ) 2 NN ii=1 (2) Agricultural Data Analysis The crop water productivities for different crops, crop evapotranspiration, irrigation efficiency, crop production, and crop price were calculated using Eqs. 3 and 4. A comparison was made between the 165

3 International Journal of GEOMATE, Feb., 218 Vol.14, Issue 42, pp principal crops in terms of crop water productivity and the profit-water ratio during the dry period (March-May) according to Eq. (5): WWWW = PP WWWW (3) PPPP = WWWW CCCC (4) WWWW = (EEEE cc + PPPPPP RR) 1 EEEEEE (5) where WWWW is water productivity [kg/m 3 ], PP is crop production [kg/ha], WWWW is the water requirement [m 3 /ha], PPPP is the profit-water ratio [$/m 3 ], CCCC is crop price [$/kg], EEEE CC is crop evapotranspiration [mm/year], PPPPPP is percolation and seepage [mm/year], RR is effective rainfall [mm/year], and EEEEEE is irrigation efficiency. 3. RESULTS 3.1 Rainfall and Evapotranspiration Rainfall (%) Annual rainfall Fig.2 Annual rainfall and anomaly rainfall in relation to the average rainfall from 1961 to 214 (raw data from Mopti met station). The daily reference evapotranspiration (EEEE ) in the Inner Delta is very high, particularly during the dry season (March May). The annual EEEE ranges from 4.72 mm/day in August to 8.63 mm/day in April (Fig. 2). ET (mm day -1 ) Anomaly Years Rainfall (mm) Month Fig.3 Daily average EEEE at Mopti Station (Inner Niger River Delta) during 215 (Source: FAO CLIMWAT) Hydrology of the Niger River To characterize the hydrological regime of the Niger River, the Koulikoro station was selected for statistical analysis; it is located approximately 2 km upstream from the Markala dam. The Koulikoro station has been operational since 197 and has provided a continuous data set since its inception. This station, therefore, allows for the characterization of the hydrology of the Niger River with an acceptable level of precision. water flow (m 3 s -1 ) 2, 1,7 1,4 1,1 8 5 Average flow... Actual flow Hydrological years Fig.4 Flow characteristics of the Niger River before and after the construction of the Sélingué dam in Koulikoro located 2 km upstream of the Markala dam. (a) Natural flow conditions, (b) flow conditions after the Sélingué dam construction in During the period between 197 and 1982 and prior to the construction of the Sélingué dam, the highest flow rate recorded was 7,586 m³/s in Following the dam construction between 1982 and 214, the highest flow rate of 5,5 m³/s was recorded in September 21. According to the historical variation in the hydraulic flow of the Niger River from 196 to 215, the flow may be classified as follows (Fig. 4): A period of high flow from 196 to 1969 with an annual average flow rate of 1,654 m 3 /s. Two periods of average flow ( and 1995 present) with an annual average flow rate between 1,226 and 1,31 m 3 /s. A period of low flow from 1982 to 1994 with an annual average flow rate of 776 m 3 /s. Figure 5 (b) clearly shows the increase in water intake and water loss between Koulikoro and Ke- Macina during the period of low flow despite the improvement in the Niger River flow in comparison with the situation in the 197s and 198s. The water-loss gap between water inflow and outflow of the river in this section changed from less than 2% in the 196s to 7% today during the low-flow period. The percentage of water levy by Office du Niger River ranges from an average of 3% in September to 69% in May. A minimum flow rate of 4 m³/s was

4 International Journal of GEOMATE, Feb., 218 Vol.14, Issue 42, pp established downstream of the Markala dam through an agreement between the Governments of the NBA countries. Despite this agreement, recent hydrometric surveys at the Markala-downstream station show that, at present, the minimum flow conditions are not maintained continuously. For the last five years ( ), the flows recorded downstream of the dam were less than 4 m³/s for an average of 73 days per year (source: Office du Niger). Q (m 3 s -1 ) Q (m 3 s -1 ) inflow (Koulikoro) 3, (a) 2, 1, (b) Hydrological years outflow(kemacina) Fig.5 Inflow and outflow at the Markala dam located upstream of Inner Delta (for the period ). (a) High-flow period (from June to February), and (b) low-flow period (from March to May). The inflow was measured at the Koulikoro gauging station 2 km upstream from the Markala dam and the outflow was measured 3 km downstream from the Markala dam Impact of Rainfall on the River Flow Figure 6 illustrates a positive partial association and a non-linear association between rainfall and river discharge in the Inner Delta with a correlation coefficient compute from equation 1 with a valuerr XX,YY = tends to. Annual Daily Mean Discharge (m 3 s -1 ) Rainfall (mm/year) Fig.6 Scatterplot of rainfall and river discharge in the Inner Delta from 196 to 215. The discharge was measured at the Ke-Macina gauging station (located in the Inner Delta) and the rainfall was measured at Mopti, located at the center of the Inner Delta Inner Delta Flooded Area, the Ecosystem and Office du Niger Agriculture pattern Muriel Bergé-Nguyen and Jean-François Crétaux [6], used a simple combination of a threshold technique performed on the MODIS Flood area of Niger River Inner Delta Fig.7 Change noted in the Inner Delta flooded area between 197 and 214 using ArcGIS (Black: both March 197 and April 214, Gray: April 214 only). 167

5 International Journal of GEOMATE, Feb., 218 Vol.14, Issue 42, pp Band 5 and Normalized Difference Vegetation Index (NDVI) to delineate the shallow, sediment laden, open waters of the IND flood plain in short term from 2 to 214. As result, they found that the inter-annual flooding peak appears in the year. 2, and 27. In this paper, remote sensing data and aerial photographs of the dry period of 197 and 214 were analyzed using ArcGIS. The results indicate that 16,41 km² of the maximum flooded area of 2,851 km² of the Inner Delta between the period 197 and 214 were lost, representing a change of 23% over the last four decades (Fig. 7). During the same period, the irrigated area of Office du Niger increased by 67% (from 58,287 to 138,418 ha). From 2 to 214, the total cultivated area during the dry period increased from 17,12 ha (34% DC, 32% of rice and 34% Sugarcane) to 43,73 ha (24% DC, 39% rice and 37% Sugarcane), as shown in Fig.8. ( 1 ha) 5 diversification crops 4 Rice fild 3 Sugar Cane Total Years Fig.8 Evolution of diversification crops, sugarcane, and rice cultivation field surface area during the dry period from 2 to 214 (data source: Office du Niger annual activities reports from 21 to 214). WPR ($ m -3 ) PWR:Profit-water ratio WP: Water Productivity WP (kg m -3 ) Fig.9 Profit-water ratio and crop water productivity for paddy rice, sugarcane, and diversification crops, such as vegetables (onions, tomatoes, and sweet potatoes), during the 214 dry period. 168 Using data on evapotranspiration, efficiency of irrigation systems, crop yields, and crop price data for the dry season of 214, a comparison was made between some principle crops based on crop water productivity and the profit-water ratio (Fig. 9). Figure 9 clearly indicates that paddy rice and sugarcane are less profitable in terms of water productivity (WP) and the profit-water ratio (PWR) than diversification crops. Paddy rice has the lowest benefit (WP =.24 kg/m 3 and PWR =.9 $/m 3 ) while onion and potato have the highest water productivity (WP = 3.86 and 3.51 kg/m 3 ), and garlic has highest profit-water ratio (PWR = 3.13 $/m 3 ). 4. DISCUSSION The rapid development of the large-scale schemes in the Office du Niger area, which are irrigated upstream, may have a significant impact on the Niger River s hydrology, as well as the floodplain and the ecosystem of the Inner Niger Delta. In this study, changes in the Inner Niger Delta as result of the expansion of the irrigated area and cropping pattern of Office du Niger were evaluated. The 196s coincided with a period of increased rainfall. However, during the 197s and 198s, a large rainfall deficit was recorded that resulted in a great drought in the Sahel countries. Sahel rainfall has been linked to Atlantic as well as Mediterranean SSTs (Sea Surface Temperatures) via evaporation rates and the supply of moisture [7] Recently, the variability in the rainfall in the Inner Niger Delta has increased, although the level remains below the average of 646 mm/year, with a minimum of 39 mm recorded in 198 and a maximum of 957 mm recorded in 1999 (Fig. 2). The rainfall in the catchment area, however, does not significantly affect the water level of the Inner Delta floodplain (Fig. 6). The Sélingué reservoir for hydropower production has changed the flooding curve. The peak level is reduced because the reservoir is filled in the early wet season and emptied in the dry season by which the river flow of the Niger became twice as high in April and May. Therefore, the relationship between the water level in the early wet season and the peak flood level has changed [8]. The current water allocation rules prioritize irrigation water demands in order to secure food production and alleviate poverty in the long term. This makes irrigated agriculture in the Niger River Basin insensitive to decreased runoff as a result of the projected climate changes, but it places pressures on the existing reservoir systems to provide a reliable water supply for hydro-

6 International Journal of GEOMATE, Feb., 218 Vol.14, Issue 42, pp electricity production, navigation, and environmental flows [9]. During the high-flow season from June to February, almost all the crop cultivated is paddy rice and sugarcane in Office du Niger (118,418 and 16,276 ha in 214, respectively) and other irrigated areas upstream of the Inner Niger Delta. Despite the high demand for water for paddy rice and sugarcane, the impact on the Niger River flow, which can reach more than 5,5 m 3 /s, remains very low (Fig. 5a). On the other hand, during dry periods when the upstream flow rate is below 2 m 3 /s (Fig. 5b), the cultivation of paddy rice and sugarcane (both high water consumption crops) increased instead of the diversification crops (DC) (onion, garlic, tomatoes, corn, potatoes etc.) as shown in Figure 8. In the past, paddy rice cropping was avoided during this season. However, since the year 2 the Malian government has decided to introduce paddy double cropping, which increased from 5,43 ha in 2 to 17,37 ha in 214 with a peak of 2,661 in 212 (available data). The sugarcane cultivation area also increased during that same period, from 5,8 ha to 16,276 ha. The cultivated area of diversification crops, which are the alternative to paddy rice during the dry season, resulted in the highest profit economically and in terms of water savings (Fig.9). However, it does not follow the trend, as more farmers prefer paddy rice. There are four main reasons for the farmers reluctance: No proper irrigation system is available to small farmers (use of containers is prevalent), Access to the market is very difficult during the harvest time, The harvest occurs at the same time resulting in a low price on market, The lack of refrigerated storage, and processing and packaging industries. To minimize the impact of Office du Niger on the Inner Delta, the following actions are required: Limiting paddy rice cultivation during the dry period (March to May), Limiting the extent of sugarcane fields, Changing of crop pattern during the dry period and opting to grow diversification crops (vegetable and others), Reducing the length of rice growth stage by using new varieties. 5. SUMMARY At present, water has become a constraining factor in the development of irrigated agriculture in Mali and the preservation of the Inner Niger Delta ecosystem. After the major droughts in the 197s and 198s, rainfall in the Inner Delta region has improved over the last decade. This condition, however, remains fragile as it has been impacted by climate change (Fig. 2). Despite the recent improvements in the upstream flow characteristics of the Niger River, water reaching the Inner Delta is reducing. This occurs mainly during the dry season (March-May) and is largely due to water withdrawals for irrigation as a result of paddy rice and sugarcane cultivation located between Koulikoro and Markala as well as between the recently constructed dams of Talo and Djenné on the Bani (tributary river) (Fig. 5 and 7). During the last three decades, the floodplain of the Inner Niger Delta has been reduced by 23%, and the irrigated area has increased by 51%. To formulate a balance between the conservation of the Inner Niger Delta floodplain and the development of irrigated agriculture, some action needs to be taken. Suggestions include the following: limiting the area available for sugarcane, reducing rice to vegetable crops during the dry period, and reducing the rice growth stage through the introduction of new varieties. 6. ACKNOWLEDGMENT Our warm thanks to Office du Niger, Mali s National Direction of Hydraulic for their support in terms of providing some data. Thanks to the Laboratory of Forest Resources of Mie University for their help in remote sensing data analyzing. 7. REFERENCES [1] United Nations Development Program (UNDP), Human Development Report 215 Work for Human Development, 215, pp [2] Institute of Statistic-Mali, Modular and Permanent Survey of Households(MPSH) First Report, Aug. 216, pp Institut Statistique du Mali, Enquete Modulaire et Permanente aupres des Menages (EMOP), Rapport analyse premier passage, Août 216, pp [3] Coulibaly A., Agriculture Irriguee et les Perspectives Economies d Eau au Mali, International Journal of Revue HTE, Vol. 141, Dec. 28, pp [4] Lemly A.D., Kingsford R.T., Thompson J.R, Irrigated Agriculture and Wildlife Conservation: Conflict on a global scale, International Journal of Environ. Manage, Vol. 25, No 5, 2, pp

7 International Journal of GEOMATE, Feb., 218 Vol.14, Issue 42, pp [5] Naghettini M., Book Fundamentals of Statistical Hydrology, Springer, 217, pp [6] Muriel B.N., Creteaux J.F., Inundations in the Inner Niger Delta: Monitoring and Analysis Using MODIS and Global Precipitation Datasets, Remote Sensing Journal, issue 7, 215, pp [7] Reindert J., Haarsma F., Selten M., Suzanne L. W., Michael K., Sahel rainfall variability and response to greenhouse warming, Geophysical Research Letters, Vol 32, L1772, 25, pp.1-4. [8] Zwarts L., Predicting the flood in the Inner Niger Delta, A&W-report 1927, commissioned by Wetlands International, Realised by Altenburg &Wymenga Ecological Consultants, 213, pp [9] Grijsen J. G., Brown C., Tarhule A., Ghile Y. B., Taner Ü., Talbi J. A., Doffou H. N., Guero A., Dessouassi R. Y., Kone S., Coulibaly B. N., Harshadeep For Chapter in a Book, Climate variability regional and thematic patterns, Published by INTECH, 213, pp Copyright Int. J. of GEOMATE. All rights reserved, including the making of copies unless permission is obtained from the copyright proprietors. 17